1. Field of the Invention
The present invention relates to a method for molding an article integrated with a multi-layer flexible circuit and an apparatus for carrying out the method and more particularly, to a method for embedding a multi-layer flexible circuit in a product by injection molding and an apparatus therefor.
2. Description of the Related Arts
Conventionally, a molded circuit board (MCB) is known. That is, a printed circuit board (PCB) is embedded in a product. Generally, the MCB is obtained by a process of injection molding. If a product including the MCB is complicated three-dimensionally, a flexible printed circuit board may be used as a PCB.
A circuit pattern is formed on a single layer by printing method to form a flexible printed circuit. But hitherto, a multi-layer flexible printed circuit has not been formed. The multi-layer flexible printed circuit means a flexible printed circuit in which the wiring pattern of each layer is electrically conductive. The reason the method for forming the multi-layer flexible printed circuit has not been developed so far is because a material consisting of a film is flexible. That is, it is very difficult to prevent the dislocation of each layer from each other layers when films are laminated on each other. More specifically, it is difficult to electrically connect the patterns of layers with each other pattern with each layer placed in position.
A known method forms a multi-layer printed circuit as follows: That is, a pattern is formed on a hard substrate consisting of, for example, ceramic or glass epoxy resin; a plurality of printed circuit boards is laminated on each other; through-holes penetrating through the pattern of each layer are formed; and conductive paste is charged into the through-holes. Since the multi-layer printed circuit thus formed includes a hard substrate, it is possible to laminate layers on each other at predetermined positions. Therefore, the pattern of each layer can be electrically connected with each other accurately. Although a plurality of layers can be laminated on each other, a hard substrate is used, which means that the configuration of the multilayer printed circuit is flat. Thus, this method is inapplicable to the formation of a molded circuit board complicated three-dimensionally.
The flexible printed circuit used in the conventional MCB is suitable for a mass-production because the circuit pattern is formed by printing. However, means for effectively forming the MCB according to varied circuit patterns have not developed yet. Needless to say, means for forming a multi-layered MCB capable of coping with varied circuit patterns have not been developed either.